Note: Where available, the PDF/Word icon below is provided to view the complete and fully formatted document
Disclaimer: The Parliamentary Library does not warrant or accept liability for the accuracy or usefulness of the transcripts. These are copied directly from the broadcaster's website.
Orchids - now thought to date back to the din -

View in ParlViewView other Segments

Robyn Williams:You've been asked this question before; why are so many human beings so passionate
about orchids?

Mark Chase: I think a lot of it has to do with the fact that they have these incredibly complex
flowers, and they're not only beautiful but they're also very intricate. You can find even the very
small ones with all this detailed structure in them. I always say it's a bit like the Dr Seuss's
book Horton Hears a Who! that if you see this little orchid flower and look at it under a
microscope or something and you see this incredible detail in that flower, you know that there's a
world out there, there's an insect that operates that flower that's probably so small that it falls
beneath our notice most of the time, and it just tells you that there's a lot going on out there
that's right down in the lower limits of what we can discern. It's just fascinating when people get
keyed in to this, it's an addiction.

Robyn Williams: An addiction. Mark Chase is the keeper of the Jodrell Labs at Kew Gardens. He's
very involved, if not addicted, to orchids; how they pretend to be sexy animals, even exuding sexy
smells to dupe the insects. It seems cruel.

Mark Chase: And of course there are a number of species of orchids that are pollinated by insects
that think they're mating with a member of their opposite sex. And not only do the flowers resemble
them physically, they also produce the same pheromones. The floral fragrances mimic the pheromones
of the female of that species, so they smell right as well as look right. So I think they make
fairly convincing mimics for these insects.

Robyn Williams: It's pretty cunning, that. I wonder how it evolved.

Mark Chase: That's a very good question. We know that some of the floral fragrance components that
are part of the sexual pheromones are present in many orchids that are attracting pollinators based
on a food basis, so it smells like there should be a reward, a sugar reward. So we know that many
orchids have lost the ability to produce nectar, so they don't give a reward but they still mimic
flowers that look as though they should have a reward.

So once you start down this road of mimicking something, in this case a food reward mimic, then the
switch from that using the same floral fragrance components over into the sexual mimicry isn't such
a big step. So it's easier to see it as a series of transitions that make sense in terms of the
fact that the orchids are mimicking something, starting out mimicking other flowers that offer a
reward and then you can get this transition over into sexual mimicry.

Robyn Williams: Such immense variety. Some of them live underground. Unground orchids, who'd have
thought! Many of them, as you say, imitate insects, many of them do lots of other things. Give us
an idea of the range that you get amongst all these hundreds of different species.

Mark Chase: We think that there's pretty good evidence anyway that orchids make use of just about
every sort of animal that has ever pollinated any other family of flowering plants, and then added
some additional ones. We just had a student working on orchids on the island of Reunion in the
Indian Ocean, and she's found there that one of the species is pollinated by a thing called a rusty
cricket, and it's the first time a member of this order of insects, the grasshoppers and crickets,
which are well known to eat plants, it's the first time we found one that actually functions as a
pollinator of this species of orchid. She had to use motion sensitive cameras and night cameras to
catch this because she knew pollination was taking place but she never observed it during the
daytime, so she set this thing up, rigged it up, and caught this rusty cricket doing the job at
night.

It's not only the first time a cricket has been observed as a regular pollinator but it's also this
cricket was unknown to science before, so it's a new species of cricket as well. So she's got quite
an interesting story there about adaptation to different sorts of pollinators on this island in the
Indian Ocean. So it seems as though once you get a flower that is capable of becoming so deceptive
and so easily changeable in their morphology, their shape, then it makes possible this wide range
of adaptations to almost every sort of conceivable pollinating animal, and then some that have
never been effective as pollinators before as well.

Robyn Williams: Can they really live underground?

Mark Chase: Yes, well, the underground Australian orchids have been demonstrated to be perfectly
capable of this. First of all, in order to live underground you have to be able to get your
nutrition from something other than photosynthesis because if you're underground, no photosynthesis
can take place. So these are what are called mycoparasites, they parasitise fungi for their food,
and that sets them up then to be able to live underground. The next thing you need is a way to have
some sort of animal that lives in the soil to be an effective pollinator, and I believe that's been
demonstrated with the underground orchid in Australia that when the inflorescence flower stem
swells it actually cracks the soil and allows insects to crawl down into the flowers and pollinate
them.

Robyn Williams: So is there a continent on which you do not get orchids?

Mark Chase: Antarctica.

Robyn Williams: There are none in Antarctica at all?

Mark Chase: No, none in Antarctica, but there are orchids everywhere else, including some very
remote oceanic islands and so on.

Robyn Williams: I've got the vague idea that as the ice melts one day, peeking from the crystals
will be one rare species.

Mark Chase: There would have been orchids on Antarctica before it went into the deep freeze because
we now know that orchids have been around for a lot longer than people had thought, and so they
would have been around at the time that Antarctica still did have plants, before the circumpolar
current sent it into the deep freeze.

Robyn Williams: So what is the actual age span and what was it thought to be?

Mark Chase: Orchids as a whole had been viewed as having a very recent origin because, number one,
they have no fossil history until...well, just recently there's been a couple found but prior to
that there were no orchid fossils of anything but very recent ages and therefore it was thought
that they had recently evolved. Of course they are herbaceous plants so they don't produce woody
parts or things that would fossilise well, so it's not too surprising there are no orchid fossils
because of the structure of the plants.

And then, number two, their seeds are wind-dispersed, so it's perfectly plausible to have them
achieve a world-wide distribution at a much more recent time because they have these wind-dispersed
seeds which can be carried great distances. So those two bits of information, along with the fact
that they're so highly developed and specialised, made people think they were recently evolved. But
there was no real evidence to show that they weren't around earlier either.

So you can use a DNA based approach to do this, which is to look at the orchids relative to the
rest of the plants that they're related to, the monocots, and you can calibrate this DNA tree with
a fossil of a known age of a group that's very clear, like the palms which have a fossil history
that goes back to 92 million years ago...

Robyn Williams: Palm trees?

Mark Chase: Palm trees, yes. And using that kind of an approach we can say that the orchids have
been around longer than the palms. The family probably has its origins some time around 110 million
years ago, which is well back into the time of the dinosaurs and before Pangaea broke up. So the
orchids were around on all these continents when they were all clustered together. And we can say
also fairly clearly that the five main groups of orchids that we have today all preceded the end of
the Cretaceous, so that they were all around during the time of the dinosaurs, all the major groups
of orchids were around, despite of the fact they have no fossil record.

Robyn Williams: Mark Chase at Kew, who says the orchids, though ancient, may have proliferated in
very recent times; 25,000 species of orchids all up.